It has been demonstrated that CD8+ cytotoxic T lymphocytes (CTLs) recognize epitope peptides derived from tumor-associated antigens (TAAs) presented on MHC class I molecules, and lyse the tumor cells. Since the discovery of the MAGE family as the first example of TAAs, many other TAAs have been discovered using immunological approaches (Boon T. (1993) Int J Cancer 54: 177-80; Boon T. et al., (1996) J Exp Med 183: 725-9; van der Bruggen P et al., (1991) Science 254: 1643-7; Brichard V et al., (1993) J Exp Med 178: 489-95; Kawakami Y et al., (1994) J Exp Med 180: 347-52). Some of them are now in clinical development as targets of immunotherapy. TAAs discovered so far include MAGE (van der Bruggen P et al., (1991) Science 254: 1643-7), gp100 (Kawakami Y et al., (1994) J Exp Med 180: 347-52), SART (Shichijo S et al., (1998) J Exp Med 187:277-88), and NY-ESO-1 (Chen Y. T. et al., (1997) Proc. Natl. Acd. Sci. USA, 94: 1914-8). On the other hand, certain gene products demonstrated to be somewhat specifically over-expressed in tumor cells have been shown to be recognized as targets for inducing cellular immune responses. Such gene products include p53 (Umano Y et al., (2001) Br J Cancer, 84:1052-7), HER2/neu (Tanaka H et al., (2001) Br J Cancer, 84: 94-9), CEA (Nukaya I et al., (1999) Int. J. Cancer 80, 92-7.) and the like.
Despite significant progress in basic and clinical research concerning TAAs (Rosenberg S A et al., (1998) Nature Med, 4: 321-7; Mukherji B. et al., (1995) Proc Natl Acad Sci USA, 92: 8078-82: Hu X et al., (1996) Cancer Res, 56: 2479-83), only a very limited number of candidate TAAs suitable for treatment of cancers are presently available. TAAs that are abundantly expressed in cancer cells, and whose expression is restricted to cancer cells, would be promising candidates as immuno-therapeutic targets.
Both HLA-A24 and HLA-A0201 are common HLA alleles in the Japanese and Caucasian populations (Date Y et al., (1996) Tissue Antigens 47: 93-101; Kondo A et al., (1995) J Immunol 155: 4307-12; Kubo R T et al., (1994) J Immunol 152: 3913-24; Imanishi et al., Proceeding of the eleventh International Histocompatibility Workshop and Conference Oxford University Press, Oxford, 1065 (1992); Williams F et al., (1997) Tissue Antigen 49: 129-33). Thus, antigenic peptides of cancers presented by these HLA alleles may find particular utility in the treatment of cancers among Japanese and Caucasian patients. Further, it is known that the induction of low-affinity CTL in vitro usually results from exposure to high concentrations of peptide, generating a high level of specific peptide/MHC complexes on antigen-presenting cells (APCs), which can effectively activate these CTL (Alexander-Miller et al., (1996) Proc Natl Acad Sci USA 93: 4102-7).
Recent developments in cDNA microarray technologies have enabled the construction of comprehensive profiles of gene expression of malignant cells as compared to normal cells (Okabe, H. et al., (2001) Cancer Res., 61, 2129-37; Lin Y M. et al., (2002) Oncogene, 21; 4120-8; Hasegawa S. et al., (2002) Cancer Res 62:7012-7). This approach enables an understanding of the complex nature of cancer cells and the mechanisms of carcinogenesis and facilitates the identification of genes whose expression is deregulated in tumors (Bienz M. et al., (2000) Cell 103, 311-20). Among the transcripts identified as up-regulated in cancers, MPHOSPH1 (M-phase phosphoprotein 1; GenBank Accession No. NM—016195; SEQ ID Nos.1, 2), and DEPDC1 (DEP domain containing 1; GenBank Accession No. BM683578) have been recently discovered. See WO 2004/031413, WO 2006/085684 and WO 2007/013,665, the entire contents of which are incorporated by reference herein. DEPDC1 has been described in the context of two different transcriptional variants—DEPDC1 V1 (SEQ ID Nos.3, 4) and DEPDC1 V2 (SEQ ID Nos: 5, 6). These genes have been shown to be specifically up-regulated in tumor cells of the various cancer tissues of the cases analyzed (see below); however, Northern blot analyses demonstrate that these gene products are not found in normal vital organs (see PCT/JP2006/302684). In that immunogenic peptides derived from MPHOSPH1, and DEPDC1 may find utility in killing tumor cells expressing those antigens, these genes are of particular interest to the present inventors.
Since cytotoxic drugs, such as M-VAC, often cause severe adverse reactions, it is clear that thoughtful selection of novel target molecules on the basis of well-characterized mechanisms of action is important in the development of effective anti-cancer drugs having a minimized risk of negative side effects. Toward this goal, the inventors previously performed expression profile analysis on various cancers and normal human tissue, and discovered multiple genes that are specifically over-expressed in cancer (Lin Y M, et al., Oncogene. 2002 Jun. 13; 21:4120-8; Kitahara O, et al., Cancer Res. 2001 May 1; 61:3544-9; Suzuki C, et al., Cancer Res. 2003 Nov. 1; 63:7038-41; Ashida S, Cancer Res. 2004 Sep. 1; 64:5963-72; Ochi K, et al., Int J. Oncol. 2004 March; 24(3):647-55; Kaneta Y, et al., Int J. Oncol. 2003 September; 23:681-91; Obama K, Hepatology. 2005 June; 41:1339-48; Kato T, et al., Cancer Res. 2005 Jul. 1; 65:5638-46; Kitahara O, et al., Neoplasia. 2002 July-August; 4:295-303; Saito-Hisaminato A et al., DNA Res 2002, 9: 35-45). Of these, MPHOSPH1 (in house No. C2093) and DEPDC1 (in house No. B5860N) were identified genes over-expressed in various cancers. In particular, MPHOSPH1 was identified as over-expressed in bladder cancer, breast cancer, cervical cancer, cholangincellular carcinoma, CML, colorectal cancer, gastric cancer, NSCLC, lymphoma, osteosarcoma, prostate cancer, renal carcinoma, soft tissue tumor. Similarly, DEPDC1 was identified as over-expressed in bladder cancer, breast cancer, cervical cancer, cholangincellular carcinoma, CML, NSCLC, lymphoma, osteosarcoma, prostate cancer, SCLC, soft tissue tumor
MPHOSPH1 was previously identified as one of the proteins specifically phosphorylated at the G2/M transition and characterized as a plus-end-directed kinesin related protein (Abaza A et al., J Biol Chem 2003, 278: 27844-52). More particularly, MPHOSPH1 has been previously documented to be a plus-end-directed molecular motor that plays a crucial role in cytokinesis, and accumulates in the midzone of the spindle during anaphase to telophase in HeLa cells (Abaza A et al., J Biol Chem 2003, 278: 27844-52; Kamimoto T et al., J Biol Chem 2001, 276: 37520-8). The MPHOSPH1 cDNA encodes a 1780-amino acid protein that is composed of three domains: an NH2-kinasin motor domain, a central coiled coil-stalk domain, and a C-globular tail domain. Together, this data suggests that MPHOSPH1 is an NH2-type kinesin-related protein.
As for DEPDC1, its function remains unclear. The DEP domain contained in this protein is also found in Dishevelled, Egl-10, and Pleckstrin. The DEP domain in Drosophila dishevelled plays an essential role in rescue planar polarity defects and induces JNK signaling; nevertheless, its function in Humans has not yet been clarified. However, as disclosed in PCT/JP2006/302684, DEPDC1 siRNAs can suppress the growth of cancer cells. These results demonstrate that DEPDC1 plays an important role in growth of most cancer cells.